1. Field of the Invention
This invention relates to a laser scanning type eye fundus camera for scan projecting a laser beam onto the retina of an eye to be tested and receiving a reflected beam from the retina through a light receiving element and then color photographing the retina in accordance with a signal coming from the light receiving element.
2. Description of the Related Art
Heretofore, an illuminating light of somewhat strong (or intensified) energy has been used for projecting the same to the retina of an eye to be tested in order to photograph a retina using a conventional eye fundus camera.
The test according to this conventional method was painful to the patient both physically and mentally.
In recent years, in order to diminish this burden or pain and enhance the safety of the testing, there was proposed a laser scanning type eye fundus camera in which a laser beam is scan projected to the retina so that a strong (or intensified) energy would not be irradiated to a particular part for a long period of time. Moreover, as a color photograph obtained by illuminating the retina with a white light is useful in ordinary eye fundus testing, there has been contemplated a laser scanning type eye fundus camera by which a color photograph can be taken.
As such a laser scanning type eye fundus camera which is capable of color photographing, there is one disclosed, for example, in U.S. Pat. No. 4,781,453. In this laser scanning type eye fundus camera, the retina is photographed for each frame using a laser beam of various wavelengths in the four colors of R, G, B and Y, and retina images obtained by respective wavelengths are combined to obtain one color retina image.
However, when the retina is to be photographed for each frame in sequence using four kinds of laser beams which have different wavelengths, it takes a long period of time to obtain one color retina image. In such a long period of time, there is a problem that the retina image may be changed due to movement of the eye to be tested. Therefore, it becomes difficult to obtain a clear retina image because there occurs a slippage of the respective images when such images of various wavelengths are combined.